不能字符串复制到字符串C中的数组 [英] Can't copy string to an array of strings in C

问题描述

我想通过我的链接列表遍历每个节点的字段合并为一个字符串，然后添加字符串转换成字符串数组。

I'm trying to traverse through my linked list and combine each of the nodes fields into a string, and then add the string into an array of strings.

void listToArray(){
   //create array of strings
    char *list[numNodes];
    int i = 0, n;

  while(head != NULL){
    // add string to array
    printf("[%d] %s %s:%d\n ", i, head->fileName, head->ip, head->port);
    n = sprintf(list[i], "[%d] %s %s:%d\n", i, head->fileName, head->ip, head->port);
    head = head->next;
    printf("%s\n", list[i]);
    i++;

 }

printf语句工作正常，这表明它不是节点，它是导致问题的领域，但是当我做我的sprintf语句将字符串复制到数组的索引。我得到一个分段错误。

The printf statement works fine, which shows that it is not the fields of node that are causing the problem, but when I do my sprintf statement to copy the string into the index of the array. I get a segmentation fault.

推荐答案

您只声明

char *list[numNodes];

但他们不分配内存。使用列表[I]之前与的malloc 分配内存。要知道生成的字符串，从的sprintf 尺寸使用的snprintf 。由于 user3121023 寻找我们这个功能。

but not allocate memory for them. Before using list[i] allocate memory with malloc. To know the size of generated string from sprintf use snprintf. Thanks user3121023 for finding us this function.

void listToArray(){
   //create array of strings
    char *list[numNodes];
    int i = 0, n;

  while(head != NULL){
    printf("[%d] %s %s:%d\n ", i, head->fileName, head->ip, head->port);

    n = snprintf(NULL, 0, "[%d] %s %s:%d\n", i, head->fileName, head->ip, head->port);
    list[i] = malloc((n+1)*sizeof(char));

    n = sprintf(list[i], "[%d] %s %s:%d\n", i, head->fileName, head->ip, head->port);
    head = head->next;
    printf("%s\n", list[i]);
    i++;

 }

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